We are evaluating the structure activity relationships of aminotetralins. A wide diversity of pharmacological properties is found in this series. The major classes discovered thus far include: 1) agents which are quite specific for beta 2-receptors, (2) alpha-receptor agonists, (3) dopamine receptor agonists, (4) apomorphine inhibiting agents. These agents also increase reaction times in mice to the hot plate and phenylquinone writhing tests. As to whether these agents are analgesics is yet to be determined. Two of the aminotetralins are equal to morphine in activity in the above tests. (5) At least one agent, 2-(N,N-di-n-propyl) aminotetralin is a hypotensive agent. In the dosage range of 30 micrograms/kg the compound produces approximately 15 mm.Hg. reduction in the diastolic blood pressure of the anesthetized cat. The reduction in blood pressure is accompanied by reduction in heart rate. The duration of action is about one hour. The site of action appears to involve the central nervous system. (6) Another very potent agent, 6,7-dihydroxy-2-dimethylamino tetralin, lowers heart rate and blood pressure in doses of 0.01 microgram - 1 microgram/kg. We believe that it inhibits adrenergic nerve terminals and may inhibit ganglionic transmission. We are synthesizing analogs in all of the above series so we can better appreciate the S.A.R. This is a unique series in that more different pharmacological actions are found in close analogs than with other chemical series.